1. Field of the Invention
This invention relates to power take-off units, and more particularly to a self contained power take-off which is remotely actuated, and which is specifically arranged for front mounting to an engine.
2. Description of the Prior Art
There are a wide variety of power take-off units which are used in conjunction with the power transmissions of trucks, tractors and other motor vehicles to provide auxiliary power transmission for such things as driving compressors on refrigerated trucks, operating auxiliary farm equipment, operating fire truck accessories, operating tailgates and lifts on truck and the like. Examples of power take-offs of this type are shown in U.S. Pat. Nos. 2,736,202 and 3,540,290 to Wagner wherein the power take-off are mounted on the main transmission so that an idler gear in the take-off engages a transmission gear to which the take-off has been mounted.
One of the difficulties encountered where the power input is taken from the main transmission involves the drag imposed by the power take-off unit on the transmission when a shift in gears is being made, which causes problems with synchronization, to which these Wagner patents are addressed. In the earlier Wagner patent, mechanical linkage was used between the power take-off clutch mechanism and the main power transmission clutch. In the later Wagner et al patent, improved operation was obtained by the use of a hydraulically operated clutch within the power take-off unit operated from an external source of hydraulic fluid.
For practical engineering considerations, friction disk clutches are conventionally used between the input and output shafts in power take-off units. Improvement in the wear compensation of such clutching devices is another area of development in this art as shown in U.S. Pat. No. 3,724,620 to Benson, Jr.
With the development of in-line input and output shaft power take-off devices which can be directly connected to the engine, such as that shown in the Benson, Jr. patent and U.S. Pat. No. 3,561,277 to Boyle et al, came the development and standardization to a certain extent of two speed power take-off devices such as that shown in the Boyle et al patent and in U.S. Pat. Nos. 3,507,372; 3,464,277 and 4,271,942 issued to Gilbertson et al, Longshore, and Ballendux respectively.
There have been continuing improvements and refinements in the use of internal hydraulic actuators for the disk clutch mechanism as shown in the aforementioned Gilbertson et al and the Wagner 3,540,290 patents and U.S. Pat. No. 3,209,872 to Moyer et al. In the Moyer et al patent the improvement is directed to the hydraulically operated clutch and an anti-creep braking mechanism. Also shown in Moyer et al is an internal pump and built-in valving, but an external hydraulic fluid source is necessary along with mechanical linkages for actuation of the valves.
It is to further improvements in hydraulically operated power take-offs that this invention is directed.
It is a primary objective of this invention to provide a self contained remotely actuated power take-off assembly which is adapted for front mounting to an engine.